This present invention relates to electric power generators, and more particularly, to a spring that provides an effective electrical ground path between a stator core and a stator frame.
A stator of an electric power generator generally includes a stator core and a stator frame. The stator core typically has a cylindrical shape and consists of a stack of insulated steel laminations. Each lamination is a segment of a full circle that has slots on its inner diameter to accommodate a stator winding and dovetail slots on its outer diameter.
A plurality of key bars are connected (e.g., welded) to the stator frame. Each key bar includes a dovetail which provides structural support for the stator core. As the stator is assembled, each dovetail slot of a respective lamination engages a corresponding dovetail. A sufficient clearance must be provided between a portion of each lamination defining each dovetail slot and its corresponding dovetail to allow for the proper assembly of the stator considering the location and dimensional tolerances of the key bar and laminations. That is, the clearance between the three faces of each lamination forming each dovetail slot and the opposing faces of the key bar defining the dovetail must be sufficient to allow for assembly of the stator. This clearance, however, must be small enough so that each lamination can contact the corresponding dovetail in the dovetail slot to provide an electrical ground path therebetween. This small clearance between the three faces of each dovetail and corresponding lamination varies randomly due to the location and dimensional tolerances of the dovetail and dovetail slot. Due to this variable clearance, the actual contact locations between each lamination and corresponding key bar (and hence the effective contact locations between the stator core and stator frame) are randomly distributed. These randomly distributed contact locations provide the grounding of the stator core to the stator frame.
It would thus be beneficial to increase the size of the dovetail slots of the laminations to allow for a faster and easier assembly of the stator and to provide a ground circuit which enables effective grounding of the stator core to the stator frame.
In an exemplary embodiment of the invention, a stator comprises a stator frame, at least one key bar connected to the stator frame and including a dovetail, and a stator core including at least one lamination including a dovetail slot for engaging the dovetail. The stator further comprises a spring coupled between a portion of the lamination and the dovetail to provide an electrical ground path between the stator core and the stator frame. The spring is arranged within the dovetail slot. The spring includes a leaf spring that comprises a first end, a second end and a central portion. The spring also includes a base portion and first and second side flaps. The first and second ends of the leaf spring contact the key bar and the central portion of the leaf spring is connected to the base portion. The base portion contacts the lamination. The side flaps are connected to the base portion and contact the lamination.
In another exemplary embodiment of the invention, the spring which provides the electrical ground path between the stator core and the stator frame includes a base portion that contacts the lamination and at least one prong. The prong comprises a first end that is connected to the base portion and a second end that is arranged spatially apart from the base portion. The second end contacts the dovetail of the key bar. The spring can include a plurality of prongs each of which is aligned along a single axis that extends parallel to the length of the base portion, or alternatively, a plurality of prongs some of which are aligned along a first axis that extends parallel to a length of the base portion and others of which are aligned along a second axis that extends parallel to the length of the base portion.